CONN 

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43 

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no.107 


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O.  E.  S.  Library.  Cop.  2,  f\0  ,  |  0^ 


THE 


Connecticut  Agricultural  Experiment  Station, 

NEW    HAVEN,    CONN. 


BULLETIN     No.     107 

DISTRIBUTED  APRIL  15th.  1891. 


The  Bulletins  and  Reports  of  this  Station  are  mailed  free  to 
evert/  citizen  of  Connecticut  who  applies  for  them  seasonably. 


THE    CONNECTICUT    SPECIES    OF  GYMNO- 
SPORANGIUM    (CEDAR   APPLES). 


THE   CONNECTICUT   SPECIES   OF    GYMNOSPORAN- 
GIUM  (CEDAR  APPLES). 

By  Roland  Thaxteb,  Mycologist, 

So  much  has  been  written  in  popular  and  scientific  literature 
concerning  the  so-called  Cedar  Apples  and  their  connection  with 
the  production  of  certain  rusts  on  fruit  trees  and  elsewhere,  that 
it  is  unnecessary  here  to  give  more  than  a  general  statement  of 
the  facts  which  should  by  this  time  be  familiar  to  agriculturalists 
generally  or  at  least  to  fruit  growers  who  are  directly  interested 
in  the  matter.  The  general  facts  referred  to  are  as  follows. 
Towards  the  end  of  spring,  usually  in  early  May,  and  during 
rainy  weather,  the  fungus  which  produces  the  well-known  distor- 
tions (cedar  apples)  just  mentioned,  protrudes  from  them  in  the 
form  of  orange-colored  gelatinous  masses,  the  orange  color  being 
chiefly  due  to  vast  numbers  of  fungus  spores  formed  on  the  sur- 
face of  these  masses,  and  known  as  teleittosptores.  These  teleuto- 
spores  germinate  rapidly,  without  becoming  detached  from  the 
swollen  masses,  and  give  rise  each  to  a  number,  sometimes  as 
many  as  a  dozen,  small  secondary  spores  which  are  discharged 
into  the  air  from  the  sides  of  short  threads  protruding  from 
them  at  various  points.  These  secondary  spores  (sjyoridia) 
falling  into  the  air  are  blown  to  apple  or  quince  trees  or 
some  other  plant  of  the  same  family,  and  adhering  to  the  surface 
of  the  tender  leaves  or  shoots  germinate  in  their  turn,  and  entering 
the  plant  tissues  produce  in  and  upon  them  the  second  or  rust 
condition  of  the  fungus,  known  as  the  Roestella  stage.  The  rust 
first  shows  itself  as  an  orange  or  yellow  spot  on  the  upper  side  of 
a  leaf  for  instance,  in  which  cavities  are  formed  producing  certain 
bodies  (spermatid)  of  unknown  function,  while  subsequently 
after  a  period  of  time  varying  in  different  species  from  ten  days 
to  three  or  even  four  months  the  Roestelia  appears  in  the  form 
of  tooth-like  projections  from  the  under  side  of  the  same  spot. 
These  projections  contain  great  quantities  of  spores  which  are 
discharged  into  the  air,  and  blowing  back  to  the  cedars  and  ger- 
minating upon  them  enter  their  tissues  and  give  rise  to  new 
oedar  apples  which  again  reproduce  the  rust  and  so  on. 


3 

'Clio  object  of  the  present  bulletin  is  to  call  attention- to  experi- 
ments which  have  been  carried  on  at  this  Station  in  regard  to  the 
relations  of  the  different  species  of  cedar  apples  to  the  various 
forms  of  rust  or  Roestelia  which  they  produce,  and  more  espe- 
cially to  the  development  of  the  so-called  "  bird's  nest "  Gymno- 
sporangium, the  characteristic  distortions  of  which  are  so  familiar 
as  to  need  no  further  description.  Although  so  common  a  species, 
the  experiments  and  observations  of  the  writer  have  demonstrated 
that  it  has  been  hitherto  undescribed,  owing  to  various  confusions 
which  need  not  here  be  dwelt  upon,  and  the  appropriate  name 
nidus-avis  (bird's  nest)  is  here  proposed  to  distinguish  this  char- 
acteristic and  strictly  American  form.  The  interest  in  the  sub- 
joined account  is  therefore  rather  scientific  than  economic,  except 
in  so  far  as  it  enforces  the  already  well-known  fact  that  to  avoid 
certain  rusts  which  are  often  serious  on  apple,  quince  or  pear  trees 
as  well  as  on  hawthorn  used  for  ornamental  or  other  purposes 
and  several  related  plants,  it  is  necessary  to  cut  down  adja- 
cent cedars  as  far  as  is  practicable  ;  for  although  it  has  been 
shown  that  infection  from  cedars  may  take  place  at  a  distance  of 
eight  miles,  the  virulence  of  the  disease  is  of  course  proportionate 
to  the  proximity  of  the  cedars. 

We  have  in  Connecticut,  so  far  as  is  now  known,  seven  distinct 
species  of  Gymnosporangium  :  two  upon  the  white  or  swamp  cedar 
(Cupressus  thy oides),  neither  of  which  are  economically  impor- 
tant, one  peculiar  to  the  common  juniper  {Jxmiperus  communis), 
three  upon  the  red  cedar  {J.  Virginiana),  and  one  occurring  on 
both  the  last  named  plants  ;  the  last  five  species  all  possessing 
more  or  less  economic  interest,  from  the  rusts  which  they  are  likely 
to  produce.  The  writer  has  continued  experiments  on  all  these 
species  for  the  past  five  years,  and  has  succeeded  by  artificial  cul- 
tures under  test  conditions  in  connecting  all  but  one  of  them  (  Gym- 
nosporangium Ellisii)  with  its  proper  rust,  making  at  the  same 
time  a  critical  study  and  comparison  of  the  different  forms  and 
stages.  In  a  paper  on  the  subject  published  in  the  Botanical  Ga- 
zette (vol.  xiv,  No.  7)  attention  was  called  (p.  169  and  172,  note) 
to  the  fact  that  the  so-called  bird's  nest  Gymnosporangium  of  the 
red  cedar,  which  had  hitherto  been  confused  with  another  Ameri- 
can (G.  clavipes)  as  well  as  with  a  European  species  (G.  coni- 
cum),  was  shown  by  cultures  made  at  this  Station  and  at  Cam- 
bridge as  well  as  by  observations  made  in  the  vicinity  of  New 
Haven,  to  be  a  distinct  and  peculiarly  American  form  as  above 


stated.  The  writer  therefore  feels  justified  in  publishing  the 
present  preliminary  note  in  order  to  ensure  for  the  Station  as 
well  as  his  own  studies  and  observations  whatever  credit  may 
pertain  to  the  solution  of  a  problem  in  mycology  which  has 
offered  considerable  difficulties  and  demanded  much  careful 
thought  and  work. 

In  regard  to  the  remaining  species  of  Gymnosporangium  it 
may  be  mentioned  in  passing  that  the  experiments  performed  by 
the  writer  before  he  became  connected  with  this  Station  have 
been  repeated  here  in  the  case  of  G.  macr&p>us,  G.  globosum,  G. 
biseptatum  and  G.  clavariaeforme,  the  failure  of  cultures  with  G. 
Ellisii  on  the  two  occasions  when  they  were  attempted,  having 
been  directly  traceable  to  the  use  of  teleutospores  which  were  not 
in  good  condition  for  cultures,  the  species  not  being  readily 
obtainable  in  a  fresh  state.  In  the  case  of  G.  macropus,  G. 
clavariaeforme  and  G.  biseptatum  results  were  obtained  identical 
with  those  previously  published  by  the  writer,  while  in  the  case 
of  G.  globosum  certain  additional  facts  were  ascertained  ;  namely, 
that  perhaps  the  most  common  orange  rust  of  apples  in  this  state 
is  undoubtedly  caused  by  this  species.  This  rust,  which  has  been 
referred  to  in  previous  papers  as  " lacerata  z"  was  induced  by 
inoculation  with  sporidia  from  G.  globosum  on  three  seedling  rus- 
sets, the  inoculation  being  made  in  the  greenhouse  by  forcing 
the  cedar  apple  as  well  as  its  host  so  early  in  the  spring  that  all 
possibility  of  accidental  mixture  was  avoided.  Sperraogonia 
appeared  the  first  week  in  April,  the  infection  having  been  made 
late  in  March,  and  perfect  and  typical  aecidia  were  developed 
early  in  July.  In  addition  to  the  cultures  of  G.  globosum  which 
were  made  on  these  apples,  two  plants  of  the  mountain  ash  (Pyrus 
Americana)  were  inoculated  with  the  same  Gymnosporangium  in 
April,  and  having  produced  luxuriant  spermogonia  gave  abundant 
and  well  developed  aecidia  late  in  July.  It  may  be  mentioned  in 
passing  that  these  aecidia  were  not  the  Moestelia  cornuta  which 
occurs  on  the  same  host  further  north,  but  had  all  the  characters 
of  the  Roestelia  which  follows  inoculation  by  G.  globosum  on 
other  hosts.  In  addition  to  the  above  facts  it  was  ascertained 
that  a  rust  of  quinces  and  of  Keiffer  pears  was  referable  to  the 
same  source  both  hitherto  unrecorded  hosts  for  this  species. 
Cultures  of  G.  globosum  on  Hawthorn  [Crataegus  crus-galli) 
were  also  repeated  and  produced  abundant  and  well  develojied 
aecidia  under  equally  strict  conditions,  confirming  the  writer's 
previous  statements  in  all  respects. 


Returning  to  the  "bird's  nest "  Gymnosporangium,  infections 
with  this  species  have  been  made  by  the  writer  every  year  since 
the  spring  of  1886,  in  order  to  determine  definitely  the  true  charac- 
ter of  the  rust  which  it  produced,  and  the  results  in  all  the  cul- 
tures were  identical,  as  to  the  mode  and  rapidity  of  development 
and  gross  as  well  as  microscopic  characters.  Until  1889,  how- 
ever, this  rust  had  never  been  recognized  in  nature  ;  but  as  soon 
as  search  was  made  for  it  in  the  light  of  the  results  artificially 
obtained,  it  was  found  in  abundance  near  the  Station  and  else- 
where in  the  State  growing  on  Quince,  but  most  luxuriantly  on 
the  Service  berry  (Amelanchier  Canadensis.)  Owing  to  its 
rapid  development,  the  lioestelia  matures  by  the  first  of  June, 
simultaneously  with  the  Roestelia  of  the  juniper  Gymnosporan- 
gium (G.  clavariceforme),  and  since  the  two  rusts  inhabit  both 
the  above-mentioned  host  plants,  they  often  occur  together  side 
by  side  on  the  same  leaf,  shoot  or  berry.  For  this  reason  although 
the  two  are  quite  distinct  in  gross  appearance  when  closely 
examined,  as  well  as  in  microscopic  characters,  they  have  never 
hitherto  been  distinguished  and  will  doubtless  be  frequently  met 
with  in  herbaria  under  lioestelia  "lacerata"  or  the  equally  erro- 
neous name  H.  penicillata.  The  general  habit  of  the  two  is 
much  the  same,  the  Roestelia  nidus-avis  being,  however,  slightly 
less  lacerate  than  M.  lacerata  and  much  darker  owing  to  the  rich 
rust  brown  color  of  its  spores  which  contrasts  strongly  with  the 
much  paler  dead  brown  of  the  spores  of  H.  lacerata  when  seen 
en  masse.  Microscopically  the  two  are  separated  at  a  glance,  the 
spores  of  It.  nidus-avis  being  smooth  while  those  of  H.  lacerata 
are  verruculose. 

The  Gymnosporangium  nidus-avis  it  may  be  mentioned  by  no 
means  confines  itself  to  bird's  nest  distortions,  but  may  occur  in 
isolated  areas  on  the  smaller  branches  on  which  it  produces  a 
slight  swelling  like  G.  clavipes,  or  may  attack  the  larger  branches 
and  even,  not  uncommonly,  the  main  trunk  of  the  tree  in  which 
its  perennial  mycelium  has  survived  for  years  as  a  result  of  infec- 
tion when  the  tree  was  very  small,  causing  a  conspicuous  swell- 
ing of  a  part  or  the  whole  of  the  trunk,  the  bark  of  which  in  the 
diseased  area  is  usually  very  rough.  That  these  forms  are  not 
due  to  any  species  other  than  the  nidus-avis  has  been  shown  by 
cultures. 

The  new  species  may  be  characterized  as  follows  : 


6 

Gymnosporangium  nidus-avis,  nov.  sp; 

Sporiferous  masses  when  young,  cushion  like,  irregularly  globose 
or  oval,  small  and  distinct  or  elongate  and  confluent  according  to 
the  habitat  ;  rich  red  brown  ;  when  mature  indefinitely  expanded 
by  moisture,  orange-colored.  Teleutospores  two-celled,  irregular  in 
shape  broadly  ovate  to  sub-elliptical  or  fusiform,  bluntly  rounded 
or  slightly  tapering  towards  the  apex,  symmetrical  or  often  slightly 
bent.  Average  dimensions  .055  X  .02511"11.  Promycelia  several, 
not  uncommonly  proceeding  from  either  extremity.  Pedicels 
when  young  often  more  or  less  inflated  below  the  spore.  Myce- 
lium perennial  in  leaves,  branches  or  trunks  of  Juniperus  Vir- 
giniana  very  commonly  inducing  a  "  bird's  nest "  distortion. 

JRoestelia  stage.  Spermogonia  yellowish  orange,  preceding  the 
aecidia  by  about  ten  days.  Aecidia  hypophyllous  or  more  com- 
monly on  petioles,  young  shoots  and  especially  on  young  fruit, 
densely  clustered,  brown,  at  first  subulate,  then  fimbriate  ;  the 
peridia  splitting  to  the  base  with  its  divisions  slightly  divergent. 
Peridial  cells  rather  slender;  the  ridges  somewhat  prominent,  sub- 
labyrinthif  orni,  horizontal  or  becoming  inwardly  oblique  towards 
the  extremities.  Average  measurements  (towards  the  apex  of 
the  peridia)  .07  X-0]8mra.  Aecidiospores  smooth,  spherical  or 
irregularly  oval  to  oblong,  average  diameter  25mm. 

Mycelium  annual  in  the  leaves  of  Cydonia  (quince)  and  in 
leaves,  stems  and  fruit  of  Amelanc/der  Canadensis  (Seiwice 
berry)  in  June. 


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